Technical Field
The inventive arrangements relate generally to methods and apparatus providing advanced operating features for audio only, video only and both video and audio programs recorded on disc media, for example recordable digital video discs, hard drives and magneto optical discs.
Various devices have been developed to enable consumers to record video and/or audio programs for later presentation. Such devices include tape recorders, video cassette recorders, recordable compact discs, and most recently, recordable digital video discs (DVD). Hard drives and magneto optical discs have also been used.
A DVD that can be recorded on only once, and thereafter is essentially a DVD read only memory, is referred to by the acronym DVD-R. The acronym DVD-R is also used generally to refer to the write-once, or record-once, technology. Several formats are available for DVD's to be recorded on, erased and re-recorded; that is, overwritten or rewritten. These are referred to by the acronyms DVD-RAM, DVD-RW and DVD+RW. As of this time no uniform industry standard has been adopted. The acronyms DVD-RAM, DVD-RW and DVD+RW are also used generally to refer to the respective rewritable technologies. Reference herein to rewritable DVD technology, devices and methods is generally intended to encompass all of the standards which are now being used, as well as those which may be developed in the future.
Depending upon the standard that is eventually adopted, if any, certain recording schemes used to implement various advanced features will be compatible with all devices adhering to the standard, whereas other recording schemes may prove to be incompatible due to inconsistencies with the standard. Nevertheless, a particular proprietary advanced feature incompatible with other devices can still be very desirable from a consumer's point of view. The result is merely that a recording made in accordance with an incompatible advanced feature cannot be played back on the device of a different manufacturer, even if conventional recordings are fully compatible and portable.
In many cases, the program presentations are recorded in the viewer and/or listener's absence, for presentation at a later, more convenient time. This is referred to as time shifting the program. At other times, a program is being viewed and/or listened to without being recorded, and with out any interest in a recording, but the viewer's and/or listener's attention is interrupted, for example by a telephone call or an unexpected visitor. If the viewer and/or listener is watching a television program, for example, and has a cassette tape in a VCR, or can retrieve and load such a cassette tape quickly, the program can be recorded. However, the viewer and/or listener cannot view and/or listen to the program in its entirety, and in a proper time sequence, until after the recording has been completed. The time to completion of the recording can be short or long, depending on the length of the program.
Although rewritable DVD technology is generally available, operation is limited to such basic functions as play, record, fast forward reverse and stop. Pause is available, but only as a counterpart to pause operation in a VCR, for example interrupting the play back of a prerecorded program or interrupting the recording of a viewed program to eliminate commercials from the recording. Unlike computer hard drives, recordable DVD devices have a very significant additional function, which is playing back prerecorded DVD's. Thus, there is an economic incentive to develop rewritable DVD technology, including methods and devices, that can be used instead of a computer hard drive. It is a challenge to provide such devices with improved, advantageous features without compromising the goal of decreasing costs and increasing sales. DVD machines typically have a 1× read and 1× write capability. Such devices can typically have maximum data rates for recording or playing back of approximately 11 megabits/second. Thus, a key consideration for implementing delete and undelete functions for the purposes of the present invention is the relatively slow rate for reading and especially recording data on a DVD. This slow rate is attributable in large part to the nature of the mechanical assembly of conventional DVD devices and the limitations associated with reading and especially writing data to an optical disc. Thus, conventional means for implementing copy, delete and undelete functions on a recordable magnetic media may not be suitable for DVD.
Rewritable DVD technology typically uses MPEG-2 encoders and decoders and many acronyms are encountered that are related to MPEG-2. The DVD standard, for example, calls for the video content of the disc to be divided up into video object units (VOBUs) in which each VOBU typically contains 0.4 to 1.0 seconds of presentation material. Each VOBU starts off with a navigation pack (NV_PCK or NAV_PACK). The navigation pack contains a lot of navigation information, some of which is very useful for trick modes. As used herein, trick modes refer to any operational mode for a recordable disc media other than the standard play mode. Thus, such modes can include reverse, fast forward, pause mode and so on.
The navigation pack includes presentation control information (PCI) and data search information (DSI). One example is the inclusion of the start addresses for many of the nearby VOBUs. This can facilitate jumping to the next VOBU forward or backward, or for a faster trick mode, to the second VOBU forward or backward, or to the third, etc. Another example is the inclusion of the end address for the first three reference pictures in the VOBU. This is the only clue given as to the structure of the VOBU.
Each video object set (VOBS) includes a plurality of video objects. Each video object includes a plurality of cells. Each cell includes a plurality of VOBUs. Each of the VOBUs containing the video content of the disc typically contains 0.4 to 1.0 seconds of presentation material. A typical VOBU in a commercial movie contains 0.5 second of presentation material, corresponding to one group of pictures (GOP). Each VOBU is a sequence of packs in recording order. Each VOBU starts with exactly one navigation pack and encompasses all of following kinds of packs, including a video pack (V_PCK), an audio pack (A_PCK) and a sub-picture pack (SP_PCK).
Data search information (DSI) helps the decoder to find reference pictures within the VOBU corresponding to the current Nav_Pack. DSI also helps the decoder to find VOBUs far into the future or past of presentation data, relative to the current VOBU. The VOBUs in the past relative to the current VOBU presentation are referenced in fields of the Nav_Pack known as the BWDI (backward information). The VOBUs in the future relative to the current VOBU presentation are referenced in fields of the Nav_Pack known as FWDI (forward information). One example is the inclusion of the start addresses for many of the nearby VOBUs, up to +240 VOBU forward and −240 VOBU backward directions. This can facilitate jumping to the next VOBU forward or backward, or for a faster trick mode, to the second VOBU forward or backward, or to the third, etc. The video, audio, subpicture, presentation control information and data search information are the five components of the DVD bit stream.